Re: [PATCH 10/14] xfs: document full filesystem scans for online fsck

Darrick J. Wong
2023-03-01T22:09:27Z

On Sat, Feb 25, 2023 at 07:33:38AM +0000, Allison Henderson wrote:

<snip>

> > > Mostly looks good nits aside, I do sort of wonder if this patch
> > > would
> > > do better to appear before patch 6 (or move 6 down), since it gets
> > > into
> > > more challenges concerning locks and hooks, where as here we are
> > > mostly
> > > discussing what they are and how they work.  So it might build
> > > better
> > > to move this patch up a little.
> >
> > (I might be a tad confused here, bear with me.)
> >
> > Patch 6, the section about eventual consistency?
> >
> > Hmm.  The intent drains exist to quiesce intent chains targeting
> > specific AGs.  It briefly mentions "fshooks" in the context of using
> > jump labels to avoid the overhead of calling notify_all on the drain
> > waitqueue when scrub isn't running.  That's perhaps bad naming on my
> > part, since the other "fshooks" are jump labels to avoid bouncing
> > through the notifier chain code when scrub isn't running.  The jump
> > labels themselves are not hooks, they're structured dynamic code
> > patching.
> >
> > I probably should've named those something else.  fsgates?
> Oh, i see, yes I did sort of try to correlate them, so maybe the
> different name would help.

Done.

> > Or maybe you were talking specifically about "Case Study: Rebuilding
> > Reverse Mapping Records"?  In which case I remark that the case study
> > needs both the intent drains to quiesce the AG and the live scans to
> > work properly, which is why the case study of it couldn't come
> > earlier.
> > The intent drains section still ought to come before the refcountbt
> > section, because it's the refcountbt scrubber that first hit the
> > coordination problem.
> >
> > Things are getting pretty awkward like this because there are sooo
> > many
> > interdependent pieces. :(
>
> I see, ok no worries then, I think people will figure it out either
> way. I mostly look for ways to make the presentation easier but it is
> getting harder to move stuff with chicken and egg dependencies.

Indeed. Thank you so much for your patience. :)

--D

> >
> > Regardless, thank you very much for slogging through.
> >
> > --D
> >
> > > Allison
> > >
>